This invention relates to a filtration apparatus which includes a filtration membrane and a membrane support. More particularly, this invention relates to a filtration apparatus wherein a filtration membrane is positioned between a base section and a top section wherein the base section and top section are sealed together.
Prior to the present invention, filtration apparatus have been provided which comprise a filtration membrane positioned between a base section and a top section. Inlet means were provided for introducing a liquid sample in the space between the top section and the base section and an outlet means is provided in the base so that liquid sample passes through the filtration membrane and is removed from the space and through the outlet. The membrane is sealed between the top section and base section in a manner to prevent liquid from by-passing the membrane. That is, sealing is effected so that all of the sample introduced through the inlet passes through the filtration membrane prior to passing through the outlet. These filtration apparatus are utilized to filter solvents to remove particulates which can cause plugging or contamination of downstream equipment such as analytical equipment. These filtration apparatus also can be utilized to effect sterilization of conditioning of medium, growth factors, virus, protein column eluates or the like prior to biological assay. The membrane can be sealed to an internal peripheral surface of the base or the membrane can be sealed to both the top and the base and between the two. The membrane can be heat sealed or solvent bonded to the base section as disclosed in U.S. Pat. No. 4,501,663 or the membrane, can be ultrasonically welded between the base section and top section as disclosed for example in U.S. Pat. No. 4,640,777. With prior art devices the weld is effective but only up to moderate pressures, for example between about 50 and 75 psi for polyethylene devices and between 75 and 100 psi for devices made from a polycarbonate-polyester melt alloy.
Also, it has been proposed to utilize ultrasonic welding of a top section and a base section with a membrane positioned intermediate the top section and base section. Either the top section or base section is provided with an ultrasonic energy directing means having a triangular cross section and which extends about the periphery of the top section or base section. The energy direction means focuses the ultrasonic energy to the periphery of the top or base section where the energy direction means contacts an opposing top or base section thereby to effect sealing about the periphery of the filtration apparatus. This results in adequate sealing. However the burst pressure is limited since the final bond is relatively inflexible so that it has limited capability of absorbing peel forces prior to bursting.
Accordingly, it would be desirable to provide a filtration apparatus for clarifying or sterilizing liquids which is capable of withstanding high pressure in order to reduce the risk of apparatus failure during filtration.